Indoor Air Reference Levels

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• Indoor Air Reference Levels (IARLs)
• Summary of Indoor Air Reference Levels

Indoor Air Reference Levels

Many volatile organic compounds (VOCs) are present in the indoor air of homes and other buildings in Canada, some of which may pose a risk to human health at certain concentrations. Health Canada has developed exposure limits for a small number of VOCs which were prioritized because they were identified by stakeholders and partners, or are found in indoor air in homes and other buildings in Canada, and have the potential to cause adverse health effects. To assist public health professionals who may need to assess the possible risk from exposure to other VOCs potentially found in indoor air, Health Canada has identified screening values called Indoor Air Reference Levels (IARLs). IARLs are selected for VOCs that have not been addressed by Health Canada's Residential Indoor Air Quality Guidelines.
To identify IARLs, Health Canada evaluated assessments developed by internationally recognized health and environmental organizations. Health Canada did not perform new risk assessments for the IARLs, but rather selected the most relevant reference level derived by other organizations. The IARLs listed below represent concentrations that are associated with acceptable levels of risk after long-term exposure (over several months or years) in non-occupational scenarios for each specific VOC, as determined by the organization that performed the risk assessment.

Summary of Indoor Air Reference Levels

The IARL selected for each VOC is listed in Table 1. The table also lists the organization from which each IARL was selected. The listed critical effects are the health endpoint used as the basis of the IARL, which is typically the most sensitive effect (i.e. occurs at the lowest concentration) that is considered relevant to humans.

Table 1. Indoor Air Reference Levels

VOC	CAS RN	IARL (µg/m3)	Critical effect		Reference	IARL Date
			Cancer	Non-Cancer
1,1- Dichloroethylene	75-35-4	0.06	Kidney tumours	n/a	OEHHA (2017)	2023
trans-1,2-Dichloroethylene	156-60-5	40	n/a	Immunotoxicity	US EPA (2020)	2023
1,3-Butadiene	106-99-0	1.7	Leukemia	n/a	EC/HC (2000)	2017
1,4-Dichlorobenzene	106-46-7	60	n/a	Nasal lesions	ATSDR (2006)	2017
1,4-Dioxane	123-91-1	2	Tumours at multiple sites	n/a	US EPA (2013)	2023
2-Butoxyethanol	111-76-2	82	n/a	Nasal lesions	OEHHA (2018)	2023 (updated)
2-Ethoxyethanol	110-80-5	70	n/a	Reproductive toxicity and hematotoxicity	OEHHA (2000)Footnote 1	2017
2-Ethylhexanol	104-76-7	0.4	n/a	Nasal lesions	US EPA (2019)	2023
3-Chloropropene	107-05-1	1	n/a	Neurotoxicity	US EPA (1991)	2017
Acetone	67-64-1	70 000	n/a	Developmental toxicity	VCCEP (2003)	2017
Ammonia	7664-41-7	500	n/a	Respiratory symptoms, lung function	US EPA (2016a)	2023
Aniline	62-53-3	1	n/a	Spleen toxicity	US EPA (1990a)	2017
Carbon tetrachloride	56-23-5	1.7	Adrenal gland tumours	n/a	US EPA (2010)	2017
Chloroform	67-66-3	300	n/a	Liver and kidney toxicity	OEHHA (2000)Footnote 1	2017
Cyclohexane	110-82-7	6000	n/a	Developmental toxicity	US EPA (2003a)	2017
Dichloromethane	75-09-2	600	n/a	Liver toxicity	US EPA (2011a)	2017
Epichlorohydrin	106-89-8	1	n/a	Nasal lesions	US EPA (1994)	2017
Ethylbenzene	100-41-4	2000	n/a	Kidney, pituitary gland, and liver toxicity	OEHHA (2000)Footnote 1	2017
Ethylene oxide	75-21-8	0.002	Lymphoid and breast cancer	n/a	US EPA (2016b)	2023 (updated)
Isopropyl alcohol	67-63-0	7000	n/a	Kidney lesions	OEHHA (2000)Footnote 1	2017
Isopropylbenzene	98-82-8	400	n/a	Kidney toxicity	US EPA (1997)	2017
Methyl ethyl ketone	78-93-3	5000	n/a	Developmental toxicity	US EPA (2003b)	2017
Methyl isobutyl ketone	108-10-1	3000	n/a	Developmental toxicity	US EPA (2003c)	2017
Propionaldehyde	123-38-6	8	n/a	Nasal lesions	US EPA (2008)	2017
n-Propylbromide	106-94-5	1.7	-	Neurotoxicity	OEHHA (2022)	2023
Propylene oxide	75-56-9	2.7	Nasal tumours	n/a	US EPA (1990b)	2017
Styrene	100-42-5	850	n/a	Neurotoxicity	ATSDR (2010)	2017
Tetrachloroethylene	127-18-4	40	n/a	Neurotoxicity	US EPA (2012), ATSDR (2014)	2017
Toluene diisocyanate	26471-62-5	0.008	n/a	Altered lung function	OEHHA (2016)	2023 (updated)
Trichloroethylene	79-01-6	2	Kidney tumours, Non-Hodgkins lymphoma, liver tumours	Thymus and cardiac toxicity	US EPA (2011b)	2023
Vinyl Chloride	75-01-4	1.1	Liver tumours	n/a	US EPA (2000)	2023
Footnote 1 Refers to the actual date of assessment. Toxicological reference value information was summarized from OEHHA (2015), OEHHA (2014), OEHHA (2011) and OEHHA (2008). Return to footnote 1 referrer

Contact the Air Health Science Division office if you:

• have questions about the Indoor Air Reference Levels
• would like to read the document summarizing the methodology for selection of IARLs
• have questions about the selection of an individual IARL

References

• ATSDR [Agency for Toxic Substances and Disease Registry] (2006) Toxicological Profile for Dichlorobenzenes. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. http://www.atsdr.cdc.gov/toxprofiles/tp10.pdf.
• ATSDR (2010) Toxicological Profile for Styrene. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. https://www.atsdr.cdc.gov/toxprofiles/tp53.pdf.
• ATSDR (2014) Toxicological Profile for Tetrachloroethylene. Agency for Toxic Substances and Disease Registry, US Department of Health and Human Services, Atlanta, GA. https://www.atsdr.cdc.gov/toxprofiles/tp18.pdf.
• EC/HC [Environment Canada and Health Canada] (2000) Priority Substances List Assessment Report: 1,3-Butadiene. En40-215/52E, Minister of Supply and Services Canada, Ottawa, ON.
• OEHHA [California Office of Environmental Health Hazard Assessment] (2008) Appendix D3. Air Toxics Hot Spot Program - Chronic RELs and toxicity summaries using the previous version of the hot spots risk assessment guidelines. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixd3final.pdf.
• OEHHA (2011) Appendix B. Air Toxics Hot Spot Program - Chemical-specific summaries of the information used to derive unit risk and cancer potency values. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixb.pdf.
• OEHHA (2014) Appendix D1. Air Toxics Hot Spot Program - Summaries using this version of the hots spots risk assessment guidelines. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/appendixd1final.pdf.
• OEHHA (2015) Appendix L. Air Toxics Hot Spot Program - Guidance manual for Preparation of Health Risk Assessments - OEHHA/ARB Health Values for Use in Hot Spot Facility Risk Assessments. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/crnr/2015gmappendiceslm.pdf.
• OEHHA (2016) Technical Support Document for the Derivation of Noncancer Reference Exposure Levels. Appendix D1 – Toluene Diisocyanate Reference Exposure Levels. California Environmental Protection Agency, Sacramento, CA. http://oehha.ca.gov/media/downloads/air/report-hot-spots/finaltdirelmarch2016.pdf
• OEHHA (2017) Proposed amendment to: Section 25705(b) Specific regulatory levels posing no significant risk. Vinylidene chloride. California Environmental Protection Agency, Sacramento, CA. Available at: https://oehha.ca.gov/media/isorvinylidenechloride092217.pdf
• OEHHA (2018) Ethylene Glycol mono-n-Butyl Ether Reference Exposure Levels. Technical Support Document for the Derivation of Noncancer Reference Exposure levels. Appendix D1. Air Toxics Hot Spots Program. California Environmental Protection Agency, Sacramento, CA.
• OEHHA (2022) 1-Bromopropane Reference Exposure Levels. California Environmental Protection Agency, Sacramento, CA. https://oehha.ca.gov/media/downloads/crnr/1-bprelsrpdraf041222.pdf
• US EPA [United States Environmental Protection Agency] (1990a) Toxicological Review of Aniline (CASRN 62-53-3). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0350_summary.pdf.
• US EPA (1990b) Toxicological Review of Propylene Oxide (CASRN 75-56-9). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0403_summary.pdf.
• US EPA (1991) Toxicological Review of Allyl chloride (CASRN 107-05-1). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0387_summary.pdf.
• US EPA (1994) Toxicological Review of Epichlorohydrin (CASRN 106-89-8). In Support of Summary Information on the Integrated Risk Information System (IRIS). United States Environmental Protection Agency, Washington, DC. http://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0050_summary.pdf.
• US EPA (1997) Toxicological Review of Cumene (Isopropyl Benzene) (CAS No. 98-82-8). In support of summary information on the integrated risk information system (IRIS). United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0306tr.pdf.
• US EPA (2000) Toxicological Review of Vinyl Chloride (CAS No. 75-01-4). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635R-00/004, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1001tr.pdf.
• US EPA (2003a) Toxicological Review of Cyclohexane (CAS No. 100-82-7). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-03/008, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1005tr.pdf.
• US EPA (2003b) Toxicological Review of Methyl Ethyl Ketone (CAS No. 78-93-3). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA 635/R-03/009, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0071tr.pdf.
• US EPA (2003c) Toxicological Review of Methyl Isobutyl Ketone (CAS No. 108-10-1). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-03/002, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0173tr.pdf.
• US EPA (2008) Toxicological Review of Propionaldehyde (CAS No. 123-38-6). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/003F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1011tr.pdf.
• US EPA (2010) Toxicological Review of Carbon Tetrachloride (CAS No. 56-23-5). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/005F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0020tr.pdf
• US EPA (2011a) Toxicological Review of Dichloromethane (Methylene Chloride). (CAS No. 75-09-2). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-10/003F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0070tr.pdf.
• US EPA (2011b) Toxicological Review of Tricloroethylene (CAS No. 79-01-6). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-09/011F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0199tr.pdf.
• US EPA (2012) Toxicological Review of Tetrachloroethylene (Perchloroethylene) (CAS No. 127-18-4). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-08/011F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0106tr.pdf.
• US EPA (2013) Toxicological Review of 1,4-Dioxane (CASRN 123-91-1). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-11/003F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0326tr.pdf.
• US EPA (2016a) Toxicological Review of Ammonia (CASRN 7664-41-7). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-16/163Fa, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0422tr.pdf
• US EPA (2016b) Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide (CASRN 75-21-8). In Support of Summary Information on the Integrated Risk Information System (IRIS). EPA/635/R-16/350Fa, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf.
• US EPA (2019) Provisional Peer-Reviewed Toxicity Values for 2-Ethylhexanol (CAS RN 104-76-7) [Noncancer Inhalation Values]. EPA/690/R-20/006F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/pprtv/recordisplay.cfm?deid=349934
• US EPA (2020) Provisional Peer-Reviewed Toxicity Values for trans-1,2-Dichloroethylene (CAS RN 156-60-5). EPA/690/R-19/001F, United States Environmental Protection Agency, Washington, DC. https://cfpub.epa.gov/ncea/pprtv/recordisplay.cfm?deid=349923
• VCCEP [Voluntary Children's Chemical Evaluation Program ] (2003) Acetone (Cas No. 67-64-1). VCCEP Submission. Voluntary Children's Chemical Evaluation Program, Washington, DC. http://www.tera.org/Peer/VCCEP/Acetone/acevccep.pdf.